Hitherto, in the case of inflation units for gas bags the electrical igniter stands far out from the side of the cylinder tube, the igniter mostly being non-releasably connected to the cylinder tube. For such an inflation unit correspondingly much installation space needs to be made available therefor in the vehicle, as a result of which space-availability may become a problem. Similar problems are also experienced in the case of linear drives, in which a projection usually protrudes from the side of the wall of a cylinder of a piston/cylinder unit in which gas generator material is accommodated and from which in turn the igniter, mostly firmly embedded in place, also protrudes. If the cylinder tube has no projection and if the gas generator material is disposed in the interior of the cylinder tube, then, however, the electrical igniter protrudes far away from the side of the cylinder tube. In addition to this, parts protruding from the side are physically endangered due to the long leverage arm involved.